The invention relates to an apparatus operated by a rechargeable battery, according to the introductory part of claim 1.
This apparatus may for example be an apparatus operated independently of the mains such as a toothcare apparatus, in particular an electrical toothbrush, a shaving apparatus, a haircare apparatus, a telephone, a small kitchen utensil or likewise.
In DE 40 22 642 there is for example shown a battery operated electrical toothbrush as well as the associated charging apparatus, wherein the latter comprises means for the symmetrical limitation of the output alternating voltage in order to reduce the susceptibility to corrosion of the connection contacts between the charging apparatus and the toothbrush. The toothbrush merely comprises a battery, a motor for driving the brush, a switch for switching the motor on or off as well as a diode.
With CH 656 987 on the other hand there is a contact-free transmission from the stationary charging apparatus to the hand apparatus, wherein the charging apparatus comprises a supply for producing a high frequency alternating voltage, whilst the hand apparatus in turn is simply constructed and apart from a secondary winding and a battery only comprises rectifier and zener diodes.
With both solutions the charging apparatus of the toothbrush for the charging of the battery makes available a voltage which adapts to the charged condition of the battery, i.e. the battery reduces the charging voltage. The charging voltage is lower, the less cells the battery comprises, the lower the nominal cell voltage and the more heavily the battery is discharged. For example the charging voltage of an already charged NiCd cell is about 1.5 V, whilst in the heavily discharged condition may sink to below 0.5 V.
In the case that the toothcare apparatus of the above mentioned documents are for example are equipped with only one battery cell, on charging accordingly also only a small voltage is available. In both cases there is therefore no possibility, apart from the battery, of supplying a further load, for example an electronic circuit, with an adequately high and at least approximately constant voltage. For example it is hardly possible at all to provide these toothcare apparatus with a charging display circuit, since the necessary supply voltage during the charging procedure is not available.